1. Field of the Invention
The present invention relates generally to methods and apparatuses for transmitting a channel sounding reference signal in a wireless communication system, and more particularly to methods and apparatuses for providing aperiodic channel Sounding Reference Signal (SRS) transmission.
2. Description of the Related Art
In general, mobile communication systems have developed to provide communication and mobility to the user. Based on the rapid development of technology, mobile communication systems have reached a stage where high speed data communication service can be provided as well as voice communication.
Currently, standardization is progressing from the 3rd Generation Partnership Project (3GPP) system to the Long Term Evolution (LTE) system as one of the next generation mobile communication systems. The LTE system corresponds to technology which implements high speed packet-based communication having a maximum transmission rate 100 Mbps faster than the currently provided data transmission rate. LTE system standardization has been almost completed. Various new technologies are applied to recent LTE communication systems while keeping pace with the completion of LTE standardization, and discussions continue for standardizing the LTE-Advanced (LTE-A) system which will significantly improving a transmission rate. “LTE system” as used herein refers to any LTE system, and thus includes both LTE and LTE-A systems.
In an LTE system, a Base Station (BS) may make a request for transmitting reference signals for channel measurement to User Equipment (UE) in order to measure uplink channels of a plurality of UEs. Available reference signal bandwidth is limited for multiplexing channel sounding reference signals, and accordingly, the reference signal cannot be transmitted at a part of the frequency band due to resolution of the reference signal bandwidth in system having a particular bandwidth. Furthermore, in order to avoid conflicts between a channel sounding reference signal transmitted by one UE and a data channel transmitted by another UE, the BS prevents data from being transmitted on the data channels of all UEs when the channel sounding reference signal is transmitted.
When the number of UEs increases, channel measurement resource regions are saturated, and the BS is required to allocate additional resources. When this happens, the uplink capacity is reduced.
Accordingly, a communication system which guarantees reference signals for more UEs and a higher transmission rate is needed to solve the above problem. More specifically, a transmission technique which neither reduces the transmission rate of the UE nor interrupts the conventional channel sounding reference signal transmission and data channel transmission is required. Furthermore, a method for indicating the transmission technique to the UE is required as well.